The disclosed technology relates generally to decoding received signals, and more particular to computing soft information for signals received from an intended source in the presence of interference from other sources.
There are several known wireless protocols for cellular and Internet systems. These wireless protocols attempt to provide high transmission reliability to wireless users, such as cellular telephone users, to prevent dropped telephone calls or poor voice transmissions. For example, to reduce the effect of interfering signals, the Global Systems for Mobile communications (“GSM”) protocol decomposes the frequency band allocated for cellular communication into seven frequency channels. This allows a cellular telephone to tune into only the appropriate channel to avoid interfering signals that are transmitted through the other six channels. However, such a communications technique forces data transmission to occur at a fraction of the maximum possible bandwidth. Reducing the bandwidth in this manner limits the maximum data rate that can be achieved by a communications network.
For conventional systems that utilize multiple receive antennas, interference cancellation is attempted by using matched filtering or linear equalization, such as zero-forcing or minimum-mean squared error equalization. Such techniques, however, may not be effective when the strength of the interference is comparable or greater than that of background noise.